Bone reconstitution in a complete osteal-periosteal discontinuity in the mid-shaft of the radius of skeletally mature dogs is the experimental model. A discontinuity just long enough to obviate spontaneous bone healing even when bridged with rigid internal plate and screw fixation is presently being used. Exogenous hormones will be administered to half of these otherwise physiologically intact skeletally mature dogs after surgical creation of the radial discontinuities and application of internal fixation to compare stimulation of bone formation in those receiving the hormones with the controls not receiving the hormones.